Iwao Hakamada is believed to be the world's longest-serving death row inmate. He has spent the past 43 years in prison in Japan, under threat of execution.

In 1968, Hakamada, a former professional boxer from Shizuoka prefecture, was convicted of the murder of the managing director of the miso (soya bean paste) factory where he worked, as well as the man's wife and his two children.

He was found guilty at an unfair trial, principally on the basis of a confession he made after 20 days of interrogation by police, and without a lawyer present. Hakamada later withdrew the confession, saying that he had been beaten and threatened.

One of the judges who convicted him, Kumamoto Norimichi, stated publicly in 2007 that he believed Hakamada was innocent in 1968, but that he had been outvoted by his colleagues.

Within months of being given a death sentence, Hakamada began to show signs of seriously disturbed behaviour. There are grave concerns about his mental health, but the prison authorities have refused his family and his legal representatives access to his medical records.

In recent months, visitors to Tokyo Detention Centre, where Hakamada is being held, have found him to be "confused, disorientated and rambling". The 75-year-old has been known to refuse his medication for hypertension and he also suffers from diabetes.

His legal team, family and supporters are calling for Hakamada to be granted a stay of execution and for him to be removed from death row. They also continue to press his claim for a retrial, citing concerns about the soundness of evidence against him.

Japan has not commuted a death sentence since 1975. Executions in the country are by hanging and are typically carried out in secret. Death row inmates are only notified on the morning of their execution and their families are usually informed only after the execution has taken place.

Prisoners live in constant fear of immediate execution. Enduring these conditions for years, or even decades, has led to extensive depression and mental illness among those sentenced to death.